- #1

WarnK

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## Homework Statement

Compute the S-operator to first order in the coupling constant lambda.

## Homework Equations

The given Lagrangian density is

[tex]L = : \frac{1}{2} (\partial_{\mu} \phi)^2 - \frac{1}{2}m^2\phi^2 + \frac{1}{2}\frac{\lambda}{4!}\phi^4 :[/tex]

where phi is a scalar field.

## The Attempt at a Solution

S = 1+iT

and I want to calculate iT to first order, which I guess is

[tex]<0|T\big( -i\int d^4x \frac{\lambda}{4!}\phi(x)^4 \big)|0>[/tex]

using Wick's theorem, how is this anything except zero? Or I'm I missing something?